Abstract:The clinker-free cement can be prepared with slag as matrix and gypsum and alkaline activator as main materials, and it is also known as low-carbon cementing material because of its remarkable carbon reduction benefit. The effects of industrial solid wastes such as fly ash, steel slag and lithium slag on the properties of gypsum slag-based cementitious materials were studied, and the hydration and hardening properties of the cementitious materials after adding solid waste were characterized by XRD, SEM and TG-DTG. The results show that the three kinds of industrial solid waste will delay the setting time and reduce the early compressive strength of the gelled material to varying degrees, but the addition of fly ash and lithium slag within 20% will improve the compressive strength in the later stage. Under the excitation of desulphurized gypsum and alkali, the materials and slag in each group promote the hydration, and the early hydration products are mainly ettringite (AFt) and hydrated calcium silicate (C-S-H) gels. With the continuous excitation of the active components in the materials in each group, the number of hydration products in the later stage increases continuously, and rod-like AFt crystals are intercalated in the C-S-H gel. As a result, the structure of the hardened paste is more dense and the strength is gradually increased.